Kinetic steam condenser

ABSTRACT

Method and system for condensing steam at any temperature, the steam being in contact with a large water surface, whereby the relative temperatures of the steam and water are regulated so that the steam is kept at under-saturation pressure and the water temperature is kept at up to 100° C.

FIELD OF THE INVENTION

The present invention relates to steam condensing and more specificallyto a steam condensing apparatus and method that save energy and increaseefficiency.

BACKGROUND OF THE INVENTION

In power plants, on ships and in industrial plants, steam condensers areused to condense the exhaust steam from a steam turbine to obtainmaximum efficiency and also to convert the turbine exhaust steam intopure water (referred to as steam condensate) so that it may be reused inthe steam generator or boiler as boiler feed water.

The most prevailing type of steam condenser are surface condenserscomprising a water cooled shell and a tube heat exchanger installed onthe exhaust steam from a steam turbine in thermal power stations. Thesecondensers are heat exchangers which convert steam from its gaseous toits liquid state at a pressure below atmospheric pressure. Where coolingwater is in short supply, an air-cooled condenser is often used.

Most of the heat liberated due to condensation of the exhaust steam insurface condensers is carried away by the cooling medium (water or air)used by the surface condenser. This heat is known to be a significantcontributor to global warming and is wasted as a source of energy.Moreover, the energy required to operate surface condensers isconsiderable.

There is need for an energy saving steam condenser, which will reducethe adverse ecological effects of surface condensers and increase theefficiency of the condensing process.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amethod of condensing steam at any temperature, the steam being incontact with a large water surface, whereby the relative temperatures ofthe steam and water are regulated so that the steam is kept atunder-saturation pressure and the water temperature is kept at up to100° C.

According to a first embodiment, the temperature difference between thesteam and the water is kept below 10° C.

According to a second embodiment, the temperature difference between thesteam and the water is kept below 5° C.

According to a third embodiment, the steam is exhaust steam from a powerplant turbine and the condensate is reused as boiler feed water.

According to a fourth embodiment, the temperature regulation comprisesheating the steam using hot gases discharged from the power plant'schimney.

According to a fifth embodiment, the temperature regulation comprisesheating the steam using fuel burning.

According to a sixth embodiment, the temperature regulation comprisesrecycling water through cooling means.

According to a second aspect of the present invention there is provideda steam condenser comprising: a steam inlet; a water inlet; a pluralityof water receiving surfaces; heating means for heating the steam;control means for maintaining a predefined temperature differencebetween the steam and the water and for maintaining the watertemperature below 100° C.; and a condensate outlet.

According to a first embodiment, the water receiving surfaces comprise aplurality of trays, installed at various heights.

According to a second embodiment, the water receiving surfaces comprisea plurality of trays installed at various heights, each tray comprisinga vertical bracket for holding water in the tray and a draining pipe fordraining excess water into a lower tray.

According to a third embodiment, the steam heating means comprise pipesleading hot gases.

According to a fourth embodiment, the hot gases are gases dischargedfrom the power plant's chimney.

According to a fifth embodiment, the hot gases are gases produced fromburned fuel.

According to a sixth embodiment, the control means comprise: means formeasuring the steam temperature in the condenser; and means forcontrolling the heating means accordingly.

According to a seventh embodiment, the control means comprise: means formeasuring the water temperature in the condenser; and means forrecycling water through cooling means.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the invention and to show how the same maybe put into effect, reference will now be made, purely by way ofexample, to the accompanying drawings.

It is stressed that the particulars shown are by way of example and forpurposes of illustrative discussion of the preferred embodiments of thepresent invention only, and are presented in the cause of providing whatis believed to be the most useful and readily understood description ofthe principles and conceptual aspects of the invention. In this regard,no attempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice.

In the accompanying drawings:

FIG. 1 is a schematic diagram of the kinetic steam condenser accordingto the present invention;

FIG. 2 is a schematic horizontal section along line 2-2 (FIG. 1) of thekinetic steam condenser according to the present invention; and

FIG. 3 is a schematic three-dimensional view of the kinetic steamcondenser according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is applicable to other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

The present invention provides a novel approach to steam condensing,whereby the steam is condensed in high temperature, as opposed tocondensing by cooling.

The kinetic steam condenser of the present invention is designed forcondensing steam discharged from power stations turbines at the end ofthe electricity production process, or for any industrial plant or shipthat use steam for operating their systems.

The kinetic steam condenser of the present invention may be operated inpower stations using fuel oil, kerosene, coal, or any other heatingmeans.

The kinetic steam condenser of the present invention uses hot steamdischarged from the turbines, thus reducing significantly the energyloss.

FIG. 1 is a schematic diagram of the kinetic steam condenser, accordingto an embodiment of present invention. The condenser (100) comprises anexternal housing (110) and an internal housing (115), with an isolationlayer (120) therebetween. External housing (110) may be constructed ofany suitable material such as concrete or metal. Internal housing (115)may be constructed of any suitable metal such as steel. Isolation layer(120) may comprise any thermal insulating material known in the art andserves to prevent heat loss and to maintain the temperature in theinternal housing.

According to one embodiment of the present invention, a combustionchamber (125) at the bottom of condenser (100) serves as heat source forthe condenser's operation, where the heat may result from burning fueloil, kerosene, coal, or any other suitable material in the combustionchamber (125).

According to another embodiment of the present invention, hot gasesdischarged from power station's chimney may be channeled throughcombustion chamber (125).

The hot gas from combustion chamber (125) flows through pipes (130),preferably mounted at the center of condenser (100) and spanning it frombottom to top. Pipes (130) may be constructed of any metal, such assteel or copper. The number of pipes and their diameters are adapted tothe specific application, taking into consideration the size of thecondenser and the required duty cycle.

The gas flows from the pipes (130) upper ends into chamber (135), fromwhich it is released via an exhaust pipe (140) into the atmosphere.

A plurality of water trays (145) are attached to internal housing (115)at different levels, surrounding the pipes (130). Each tray (145)comprises a horizontal platform (150), a vertical bracket (155) on theinner side of the platform (150) and at least one draining pipe (160)drilled through the platform (150). Draining pipes (160) serve tocascade excess water from each tray to the tray below it.

A water temperature regulating system is attached to the condenser,including a suction pipe 165, a radiator (170) for reducing the water'stemperature, a pump (175) for pumping water from the radiator (170) anda pipe (180) through which the water is returned to the condenser at thedesired temperature. The water temperature regulating system is operatedperiodically, when the water temperature in the condenser needs to bedecreased by a few degrees, as will be explained in detail below.

A steam inlet (185) on the upper part of condenser (100) allows steamfrom the power plant turbines to flow into the condenser, where it flowsfreely and is heated by the hot pipes (130).

A distilled water inlet (190) on the upper part of condenser (100)serves for inserting distilled water into condenser (100) beforeoperating it. The water inserted through inlet (190) cascades to thelower trays.

A condensate draining pipe (195) at the bottom of condenser (100) drainsthe condensed steam which is flown back to the turbine.

Thermometers (205, 210), installed inside the condenser (100), serve formonitoring the temperatures of the steam and the water, respectively,throughout the condensing process.

Air exhaust valve (215), at the upper side of condenser (100), servesfor releasing air, repelled by the incoming steam, from the internalhousing.

FIG. 2 is a schematic horizontal section of the kinetic steam condenser(100) of FIG. 1, showing the internal housing (115) and a tray (145)surrounding the central pipes (130) and having a vertical bracket (155)and drilled draining pipes (160).

The operation of the kinetic steam condenser of the present inventionwill now be explained.

The condensing process begins with distilled hot water being insertedinto the condenser (100) via water inlet (190). The water is preferablyinserted at a temperature below 90° C. The water cascades to the lowertrays, so that each tray holds a certain quantity of water.

The steam emerging from the turbines during the electricity productionprocess is at a temperature of less than 100° C. and therefore haspressure of less than 1 atm. and is on the verge of saturation.

The steam is inserted into the condenser (100) through steam inlet (185)and repels the air from within the condenser, through air exhaust valve(215).

Next, the burning chamber (125) is operated, either by burning fuel oil,kerosene, coal, or any other suitable material in it, or by channelinghot gases discharged from power station's chimney into it. The hot gasemanating from the burning chamber (125) flows into pipes (130) andheats the steam in the condenser by a few degrees.

Vapor-liquid equilibrium is a condition where a liquid and its vapor(gas phase) are in equilibrium with each other, a condition or statewhere the rate of evaporation (liquid changing to vapor) equals the rateof condensation (vapor changing to liquid) on a molecular level, suchthat there is no net (overall) vapor-liquid interconversion.

The pressure of vapors in a vapor-liquid equilibrium is calledsaturation pressure, and is constant at any given temperature.

The temperature of the water in the trays (145) is lower by a fewdegrees than that of the steam, causing the steam, which aspires to astate of saturation pressure at any given temperature, to startcondensing into the water. The condensation releases heat into the waterand raises their temperature.

The condensation creates vacuum in the condenser, which inducesadditional flow of steam into the condenser.

This process continues as long as there is a temperature differencebetween the steam and the water in the condenser, so that saturationpressure is never attained.

Thermometer (205) continuously monitors the steam temperature and theburning rate at the burning chamber (125) is adjusted accordingly, so asto prevent the steam temperature from reaching a predefined temperature.In a preferred embodiment, the steam temperature is kept below 100° C.

Thermometer (210) continuously monitors the water temperature. If thewater temperature rises above a predefined temperature, e.g. 90° C., thewater temperature regulating system is operated, whereby water from thebottom of the condenser are being pumped into radiator (170), where itis cooled by a few degrees and flows back into the condenser, via pipe(180), at a suitable temperature.

When the water/condensate level in each tray reaches the opening of thedrilled pipe (160), it flows into the tray below, and so forth. Theexcess water accumulates at the bottom of the condenser, where it flowsout via draining pipe (195) into an intermediate vessel (200), ordirectly into pipes leading to the turbine.

The large number of trays (145) result in large contact surfaces betweenthe water and the steam, thus enabling the condensation of large steamquantities. The larger the contact surface, the higher is thecondensation efficiency at any give temperature.

The method of the present invention is applicable as long as the watertemperature is kept equal to or lower than 100° C.

EXAMPLE

A power station that produces 1400 MW/hour produces 1100 Tons of steamper hour, i.e. about 306 Kg of steam per second.

If we choose to have a water surface of 30 m² for every Kg of steam persecond, we need a total water surface of 9180 m² to condense 1100 Tonsof steam per hour.

An exemplar condenser could comprise a 10 m diameter and 20 m height.160 trays may be built, at height differences of about 12 cm,surrounding the heating pipes, each tray having a surface of 60 m², sothat the total surface of the trays, which is the total water surface tobe in contact with the steam, equals 9600 m².

The kinetic steam condenser of the present invention is operable in anytemperature.

If the steam discharged from the power plant's turbines is at 80° C.,the highest efficiency will be attained by condensing it into water at80° C. Therefore, the steam will be heated by 3-5° C., and when thewater in the trays reaches 80° C., the water temperature regulatingsystem is operated so as to keep the water at that temperature.

Conversely, in conventional power stations using cooling condensers, thesteam discharged from the turbines at approximately 80° C. and 0.46 Atm.is cooled to 30° C., a process which uses huge quantities of energy. Inthe example above, the power station that produces 1400 MW/hour and 1100Tons of steam per hour would require about 160,000 m³ of cooling waterper hour.

The amount of heat lost in cooling 1100 Tons of steam from t₂=80° C. tot₁=30° C. is given by the formula: Q=mc(t₂-t₁), where c=1 is thespecific heat of water.

Q=1,100,000×1(80−30)=55,000,000 Kcal

It is well known that the burning heat of 1 Kg petroleum is 10,000 Kcal,resulting in the cooling process requiring 5,500 Kg petroleum/hour,which amounts to 132,000 Kg/24 hours or 48,180,000 Kg petroleum/year.This is on top of the huge amount of water required for the coolingprocess and a significant part of the condensing heat mK, where m is theamount of steam and K is is the amount of condensing heat per 1 Kg ofsteam.

The majority of power stations work in less than 50% efficiency,resulting in a net saving that is essentially a double of the quantitycalculated above, in the kinetic steam condenser of the presentinvention.

The amount of energy required for the operation of the condenseraccording to the present invention is approximately 550 Kg petroleum perhour, i.e. 5,500,000 Kcal/hour.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meanings as are commonly understood by one of ordinaryskill in the art to which this invention belongs. Although methodssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods aredescribed herein. In addition, the methods, and examples areillustrative only and not intended to be limiting.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined by the appended claims and includes both combinations andsub-combinations of the various features described hereinabove as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description.

1. A method of condensing steam, the steam being in contact with a largewater surface, whereby the relative temperatures of the steam and waterare regulated so that the steam is kept at under-saturation pressure andthe water temperature is kept at up to 100° C.
 2. The method of claim 1,wherein the temperature difference between the steam and the water iskept below 10° C.
 3. The method of claim 2, wherein the temperaturedifference between the steam and the water is kept below 5° C.
 4. Themethod of claim 1, wherein the steam is exhaust steam from a power plantturbine and the condensate is reused as boiler feed water.
 5. The methodof claim 4, wherein the temperature regulation comprises heating thesteam using hot gases discharged from the power plant's chimney.
 6. Themethod of claim 1, wherein the temperature regulation comprises heatingthe steam using fuel burning.
 7. The method of claim 1, wherein thetemperature regulation comprises recycling water through cooling means.8. A steam condenser comprising: a steam inlet; a water inlet; aplurality of water receiving surfaces; heating means for heating thesteam; control means for maintaining a predefined temperature differencebetween the steam and the water and for maintaining the watertemperature below 100° C.; and a condensate outlet.
 9. The steamcondenser of claim 8, wherein the water receiving surfaces comprise aplurality of trays, installed at various heights.
 10. The steamcondenser of claim 9, wherein each tray comprises a vertical bracket forholding water in the tray and a draining pipe for draining excess waterinto a lower tray.
 11. The steam condenser of claim 8, wherein the steamheating means comprise pipes leading hot gases.
 12. The steam condenserof claim 11, wherein the hot gases are gases discharged from the powerplant's chimney.
 13. The steam condenser of claim 11, wherein the hotgases are gases produced from burned fuel.
 14. The steam condenser ofclaim 8, wherein the control means comprise: means for measuring thesteam temperature in the condenser; and means for controlling theheating means accordingly.
 15. The steam condenser of claim 8, whereinthe control means comprise: means for measuring the water temperature inthe condenser; and means for recycling water through cooling means.